As Angel had explained, they had been looking for a powerful elemental that could have helped them defeat the guards. Bone Elementals were incredibly strong and could easily be snuck into the palace. In the past, there were a number of them in the cavern but they are all gone. She suspected that Rheidan had collected all of them and used them to create part of his palace. 

All of entrances to the Bone Palace were guarded by the Shadow Elemental Hybrids and there were not enough hybrids in the caverns to force their way in. So, the only way that they figured out to get in was to sneak in. The ones that they transported in with the skulls were too weak or small to take on the guards but, since the Artifact, according to legend, could change me into any elemental that I imagined, I may have a chance to defeat the guards.

“You have to try to transform. Your friends are still stuck in the Bone Palace and, eventually, Rheidan and his hybrids will find them. I don’t want to think about what would happen to them. You have to try,” she said. Before she left, she applied a salve onto my body to help protect me against the guards. “Every little bit helps”, she said.